Signal transmission cables for transmitting/receiving electrical signals generated in acoustic systems or imaging systems may be connected for use with earphones, headphones, speakers, or image display devices. Here, cables used for earphones, headphones, measuring instruments, and the like may generally have superior flexibility.
As well-known, such a cable includes a metal conductor for transmitting a signal and an insulating coating for protecting the metal conductor. Here, an insulating jacket may be additionally disposed on the insulating coating. In addition, to reduce the effects of surrounding electromagnetic noises and transmission losses, a metal shield and an insulating jacket may be disposed on the insulating coating.
Typically, an insulating coating is formed of an insulating polymer resin. The insulating polymer resin may be extruded onto the metal conductor by using an extruder to manufacture the insulating polymer coating. Well-known polyvinyl chloride (PVC)-based and non-PVC-based thermoplastic resins or thermosetting rubber such as silicone rubber may be selectively used as the insulating polymer resin used for the insulating polymer coating or the insulating jacket.
In general, typical PVC-based or non-PVC-based thermoplastic resins may be relatively inexpensive and easy for extrusion, but have poor elastic and restoring force. Typical silicone rubber-based thermosetting rubber may have elasticity and flexibility, but have relatively high frictional coefficient, low hardness, and high manufacturing costs.
As described above, in the insulation coating and insulating jacket constituting the conventional cable, it may be difficult to reduce a frictional coefficient and increase a hydrophobic property on an outer surface of the cable and by using polymers corresponding to the insulating coating and the insulating jacket.
As a result, since the insulating coat or insulation jacket that forms the outermost surface of the conventional cable has a relatively low surface frictional coefficient, the conventional cable has problems as follows:
a) The cable may be easily tangled, and it may be difficult to untangle the tangled cable.
b) If the cable moves in contact with a user's skin, the user may not feel good, and the user' skin may be damaged by surface friction.
c) When the cable contacts an external object, noises may occur by friction.
Also, since the insulating coating or insulating jacket has relatively low surface hardness, the cable may be easily damaged by external friction or a facing object.
Also, since the insulating coating or insulating jacket has relative low elastic and restoring force, if the cable is tangled once, the cable may not be easily untangled.
Also, since the insulation coating or insulating jacket has a low hydrophobic property, foreign substances may be easily attached on a surface of the cable. In addition, the cable may be easily contaminated. For example, if the foreign substances are attached once, the foreign substances may not be easily detached. Also, the cable may easily scribble by writing instruments such as ballpoint pens and the like, the scribbling marks may not be easily removed.
Also, since the surface of the insulating coating or insulating jacket has a low hydrophobic property and an absorbable property, the cable may be easily swelled or discolored by salt water or sweat.
Also, the surface of the insulating coating or insulating jacket may be easily discolored by ultraviolet (UV) rays.
Also, since the surface of the insulating coating or insulating jacket does not have a gloss, the cable may not have an elegant color.
For example, when a cable including an insulating coating or insulating jacket formed of a flexible PVC-based or non-PVC-based resin or a flexible PU-based synthetic resin is applied to earphones of smart phones, if considering a feature in which the earphones are frequently put in/out a pocket, the earphones may be easily tangled because the earphones have a relatively high frictional coefficient and low elasticity. Also, if the earphones are tangled once, it may be not easy to untangle the tangled earphones and restore the crumpled portion to its original state. Also, since the earphones have a low hardness, the earphones may be easily damaged. In addition, since the earphones have a low hydrophobic property, the earphones may be easily contaminated by foreign substances such as ballpoint pens and the like.
Also, when the earphones rub against clothes, friction sound may occur. Also, when the earphones contact a user's neck, the earphones may be easily swelled or discolored by sweat. Also, when the earphones contact a face, cosmetics cosmetized on the face may be easily stained on the earphones. Also, if the earphones are excessively exposed to the sun, the earphones may be easily changed in color, and it may be difficult to realize an elegant outer appearance and a high gloss.
The above-described problems may equally occur in cables for earphones, frequently movable cables for measuring instruments or robots, or cables for computers.